Highly active anti-retroviral therapy can effectively control virus replication in HIV-1 positive individuals. However, problems such as drug resistance and side effects often compromise the effectiveness of anti-HIV- 1 drugs. Therefore, the development of new anti-HIV agents with novel mechanisms of action is needed. In an effort to identify novel anti-HIV-1 agents, we have synthesized potent bi-functional betulinic acid (BA) derivatives that inhibit both HIV-1 entry and maturation by targeting gp120 and gag proteins. Although these small molecules inhibit HIV-1 at low nanomolarity concentrations and have different mechanisms of actions from other anti-HIV-1 drugs, the clinical potential of this class of compounds has not been evaluated. The objective of this project is to synthesize and identify potent bi-functional anti-HIV BA derivatives for further clinical development. This is a step toward our long term goal to develop anti-HIV-1 agents with novel mechanisms of action for AIDS therapy. The central hypothesis of this study is that the dual novel mechanisms of action of the bi-functional BA derivatives will allow the compounds to potently inhibit HIV-1 including strains already resistant to current anti-HIV drugs. In addition, the dual mechanisms of action are likely to slow the emergence of mutants resistant to the bi-functional BA derivatives. We plan to test this hypothesis and accomplish the objective of this study with the following specific aims: 1. To synthesize the bi-functional BA derivatives that are more potent than the current lead compounds. 2. To determine the molecular mechanisms of action and drug resistance profiles of the bi-functional BA derivatives. 3. To determine the efficacy of the bi-functional BA derivatives against HIV-1 primary isolates and bioavailability in small animals. In addition, the effect of the bi-functional BA derivatives on drug resistant viruses and HIV-1 replication in a SCID-hu mouse model will also be determined. The novel mechanisms of action and the ability to inhibit two targets make the bi-functional BA derivatives promising candidates for anti-HIV therapy. Results of the proposed study are expected to provide insights into the clinical potential of this class of compounds for AIDS therapy.